Foreplay

physical and social ossification

Bones are interesting for a variety of reasons. Like
fiberglass and other composites, they are a hybrid of glue and
grit, with collagen playing the role that epoxy resin plays in
human-made composites, and tiny mineral crystals playing
the role of the thin glass fibers. To the extent that humans have
been using composites since they first used straw brick, the
principle of combining glue and grit to get novel emergent
properties was already known to us.